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Characterizing Global Archaeocyathan Reef Decline in the Early Cambrian: Evidence from Nevada and China

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Characterizing Global Archaeocyathan Reef Decline in the Early Cambrian: Evidence from Nevada and China UNLV Retrospective Theses & Dissertations 1-1-2005 Characterizing global archaeocyathan reef decline in the Early Cambrian: Evidence from Nevada and China Melissa Hicks University of Nevada, Las Vegas Follow this and additional works at: https://digitalscholarship.unlv.edu/rtds Repository Citation Hicks, Melissa, "Characterizing global archaeocyathan reef decline in the Early Cambrian: Evidence from Nevada and China" (2005). UNLV Retrospective Theses & Dissertations. 2658. http://dx.doi.org/10.25669/4dcj-qx5g This Dissertation is protected by copyright and/or related rights. It has been brought to you by Digital Scholarship@UNLV with permission from the rights-holder(s). You are free to use this Dissertation in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s) directly, unless additional rights are indicated by a Creative Commons license in the record and/or on the work itself. This Dissertation has been accepted for inclusion in UNLV Retrospective Theses & Dissertations by an authorized administrator of Digital Scholarship@UNLV. For more information, please contact [email protected]. CHARACTERIZING GLOBAL ARCHAEOCYATHAN REEF DECLINE IN THE EARLY CAMBRIAN: EVIDENCE FROM NEVADA AND CHINA by Melissa Hicks Bachelor of Science, Geology Juniata College 1999 Masters of Science, Geoscience University of Nevada, Las Vegas 2001 A dissertation submitted in partial fiilfillment of the requirements for the Doctor of Philosophy Degree in Geoscience Department of Geoscience College of Sciences Graduate College University of Nevada, Las Vegas May 2006 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. UMI Number: 3226620 Copyright 2006 by Hicks, Melissa All rights reserved. INFORMATION TO USERS The quality of this reproduction is dependent upon the quality of the copy submitted. Broken or indistinct print, colored or poor quality illustrations and photographs, print bleed-through, substandard margins, and improper alignment can adversely affect reproduction. In the unlikely event that the author did not send a complete manuscript and there are missing pages, these will be noted. Also, if unauthorized copyright material had to be removed, a note will indicate the deletion. UMI UMI Microform 3226620 Copyright 2007 by ProQuest Information and Learning Company. All rights reserved. This microform edition is protected against unauthorized copying under Title 17, United States Code. ProQuest Information and Learning Company 300 North Zeeb Road P.O. Box 1346 Ann Arbor, Ml 48106-1346 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Dissertation Approval 4IV The Graduate College University of Nevada, Las Vegas Ma^-eh—20- -.20ûé- The Dissertation prepared by _______________ M elissa Hicks Entitled Characterizing the Global Archaeocyathan. Reef Decline in the Earlv Cambrian; Evidence from Nevada and China________________________________ is approved m partial fulfillment of the requirements for the degree of Doctor of Philosophy in Geoscience ________________ Examination Committee Chair Dean of the Graduate College Examination Committee Member Examination Committee Member A Graduate College Faculty Representative 1017-52 11 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ABSTRACT Characterizing Global Archaeocyathan Reefs Decline in the Early Cambrian: Evidence from Nevada and China by Melissa Hicks Dr. Stephen M. Rowland, Examination Committee Chair Professor of Geoscience University of Nevada, Las Vegas This study presents new data on the sedimentology of the northern Yangtze Platform, the ô^^C stratigraphy of South China and Nevada, and the decline and virtual extinction of archaeocyaths. Paleoecological, sedimentological, and chemostratigraphic data were collected from multiple localities that span from the mid-Early Cambrian of Nevada (Poleta Formation) and China (Xiannudong Formation) to the late-Early Cambrian of Nevada (Harkless Formation) and China (Tianheban Formation). Facies represented in the Xiannudong Formation describe a Bahamas-type platform for the Yangtze Platform with a static and negative ô^^C record. All four formations analyzed show a static ô^^C record that varies from slightly negative to slightly positive. This is unexpected because stasis is not observed in the composite ô^^C record of the Siberian Platform, suggesting that our data may represent intrabasinal Ô^^C records and not global. Another important feature I observed in the Xiannudong Formation is a faunal changeover from predominantly regular-type archaeocyaths in the lower Xiannudong Formation to predominantly irregular-type archaeocyaths in the upper part. This 111 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. changeover is also seen between the Poleta Formation and the Harkless Formation in Nevada. Finally, I analyzed the physical changes in archaeocyathan skeletons over time. A progressive thinning of skeletal thickness was expected, however a distinct trend of skeletal thickening was observed. Skeletal thinning was expected due to a lowered carbonate saturation state driven by rising atmospheric CO 2 . To explain thickening, I propose that irregular archaeocyaths contained photosymbionts, which are documented to counteract a lower carbonate saturation state. Irregular archaeocyaths, which inherently contain more elements in their intervallum, and hence, more soft tissue, could house more endosymbionts than regulars. Therefore, regulars declined due to the lack of abundant photosymbionts, while irregulars flourished. Currently, there is no definitive evidence to support our hypothesis that the ultimate extinction of archaeocyaths was due to increased sea surface temperatures due to the greenhouse warming effect of increased pCOz Prolonged temperatures would have increased thermal stress on the archaeocyaths until some threshold was reached in which even irregulars could not survive. This scenario may have implications for modem reef reactions to anthropogenic CO 2 and greenhouse warming. IV Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. TABLE OF CONTENTS ABSTRACT.......................................................................................................................iii LIST OF FIGURES.......................................................................................................... vii LIST OF TABLES................................ ix ACKNOWLEDGMENTS.................................................................................................. x CHAPTER 1 INTRODUCTION....................................................................................... 1 References .....................................................................................................................4 CHAPTER 2 EARLY CAMBRIAN MICROBIAL REEFS, ARCHAEOCYATHAN INTER-REEF COMMUNITIES, AND ASSOCIATED FACIES OF THE YANGTZE PLATFORM........................................................................... 6 Abstract..........................................................................................................................6 Introduction ....................................................................................................................8 Methods ....................................................................................................................... 13 Stratigraphy of the Xiannudong Formation and Paleoenvironmental Interpretation ............................................................................................. 14 Paleoenvironmental Synthesis .....................................................................................48 Implications for the Yangtze Platform ........................................................................ 51 Acknowledgments ....................................................................................................... 51 References ....................................................................................................................52 CHAPTER 3 CHEMOSTRATIGRAPHIC ANALYSIS OF EARLY CAMBRIAN MICROBIAL REEFS, ARCHAEOCYATHAN REEFS, AND ASSOCIATED FACIES IN NEVADA AND SOUTH CHINA: A SURPRISING STORY OF STASIS.........................................................57 Abstract........................................................................................................................57 Introduction ..................................................................................................................59 Methods .......................................................................................................................63 Stratigraphy and Sedimentology ................................................................................. 64 Biostratigraphy............................................................................................................ 72 Chemostratigraphic Analysis.......................................................................................74 Conclusions ................................................................................................................. 78 Acknowledgments ....................................................................................................... 79 References....................................................................................................................80
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